Over the past ten to twelve years furniture seat spring torsioning devices such as disclosed in U.S. Pat. No. 3,210,064, No. 3,388,904, and No. 3,525,514, met the industry's long sought need for deep-drop uplift at the back rail and also contributed in other ways to the luxury seat which evolved during that time frame. As eleven (11) gauge helical spring connectors became disproportionally more expensive during this period these devices have been used almost exclusively with SWING ANCHOR connecting links and radius links such as disclosed in U.S. Pat. No. 3,790,149, and depended upon kinetic energy stored in the arced sinuous spring itself to produce all upward resilience. The upholstered furniture styles most widely sold at the time developed all the back rail uplift considered desirable using such connecting links.
During the past three to four years, however, there has been a move toward the use of thicker and thicker cushions. Attractive new and thicker cushion materials, including foam rubber laminates, have necessitated the lowering of seat frame heights dramatically. As a result, an urgent need was created in such constructions for more upward resilience of a strong dynamic nature in the spring base.